With the development of technology, the application of a power battery is becoming more and more extensive, which involves production or life. The power battery is also called a secondary battery which is a rechargeable battery. The power battery is widely used. Low-capacity power battery can be used in small electric vehicles, and high-capacity power battery can be used in large electric vehicles such as hybrid or electric vehicles. When the power battery is used in groups, it is necessary to connect each power battery in series or in parallel via a bus bar. Usually, the bus bar is weld to the positive and negative terminals of the power battery. Each power battery includes a plurality of battery modules. Each battery module includes a plurality of batteries and end and side plates for fixing the plurality of batteries. The end and side plates are provided around the batteries. In the prior art, the end plates are of an integrated structure. The end and side plates are fixedly mounted by welding. As the capacity of the battery module is increasing, the batteries will expand in some cases. Thus, expansion force may be applied to the end and side plates, thereby causing the end and side plates to be easily deformed and displaced and further causing the weld between the side and end plates failure. Therefore, there is a problem that the conventional battery module has low structural strength.